There is a need in many industries to monitor locations and movement of underground structures, e.g., naturally occurring geological formations (e.g., ore bodies) or man-made buried structures (e.g., pipe lines).
For example, in the mining industry, mines are established to extract valuable materials from the ground. The ground generally includes the valuable materials (the ore) mixed with non-valuable materials (the waste rock or gangue). Historically, ore was located only as it became visible during extraction or excavation. In modern mining operations, geologists can determine the location of ore in the ground before mining commences. Geologists can generate three-dimensional geological maps of ore bodies in the ground before the excavation commences, and on an ongoing basis during excavation. Using the geological map, the mining engineers can practice “selective mining”. As mining engineers know the location of the ore body in advance, “economic ore” (i.e., at a sufficient concentration in the ground) can be excavated separately from sub-economic ore (which is insufficiently concentrated in the ground). The ore boundaries can be indicated on the ground surface (referred to as the “bench area” in an open-pit mine) to indicate the economic areas and the sub-economic areas. The economic and non-economic areas can be represented by polygons. When the rock is excavated, the rock from the sub-economic polygons can be sent to a waste dump, while rock extracted from the economic polygons can be sent to an ore processing facility.
To enable the rock to be efficiently and conveniently extracted by a digger, the rock requires blasting to break it up into a so-called “muck pile”, suitable for digging, loading and transport. During blasting, however, movement can occur in the ground, and the boundaries between the economic and sub-economic regions can move. The location of the ore bodies may then no longer correspond to the locations in the three-dimensional geological map, and it may be difficult to select digging polygons on the bench area that will provide a good separation of the ore from the waste rock. Different blasting techniques are required for each blast, depending on the blast design, blast geometry, bench geology and geometry, and mineralisation geometry. It can be difficult therefore to predict the post-blast locations of all boundaries in the ground based on the pre-blast three-dimensional geological map of the ore body. If the post-blast ore body boundary is not correctly identified, a portion of the valuable ore may be incorrectly transported to the waste dump, while additional waste rock may be transported to the ore processing facility. The loss of ore in mining, and the unnecessary processing of waste material, is referred to as “ore dilution”.
There is therefore a need to identify the location of the post-blast ore body boundary in the muck pile as accurately as possible to provide for higher efficiency mining of the ore. There may also be a need to determine the ore boundaries in the muck pile as quickly as possible after blasting to provide for rapid and efficient extraction of the ore.
It is desired to address or ameliorate one or more disadvantages or limitations associated with the prior art, or to at least provide a useful alternative.